I have a factory unlocked, not yet jailbroken iphone 3g. I am running ios 4.2.1 and firmware 5.15.04. My problem is that the edge connection keeps getting turned off randomly (rather frequently) and I need to keep toggling the airplane mode to get it back to work. I already tried resetting network settings, resetting all settings, restoring to factory settings and creating a new profile. None of it seems to work. Other iPhone users on Airtel (a carrier in India) are not having this problem. Please let me know if anything could be done?
The last thing you can try to do before sending it to repair is making a new install by Erasing All Content and Settings. There are many ways to accomplish this and many layers of wiping. One of them is through installing a new firmware (ipsw) file just in case the one iTunes download is somehow corrupted.
But doing anything beyond the regular Apple way is entirely up to you as the process are even more time consuming and not all that simple.